Molybdenum blue assay for measurement of chemical species

Abstract

A process for measuring a concentration of a chemical species in an aqueous sample employing polyvinylpyrrolidone. The process comprises: providing an aqueous sample containing the chemical species; mixing the aqueous sample with a first reagent that comprises a solution of a molybdenum VI salt to provide a first solution; mixing the first solution with a second reagent that comprises a reducing agent to form a second solution; and measuring a property of the second solution to determine the concentration of the chemical species. Polyvinylpyrrolidone is added to the aqueous sample, the first reagent, the first solution or the second solution. The intensity of light absorbed or transmitted by the second solution may be used to determine the concentration of the chemical species.

1 . A process for measuring a concentration of a chemical species in an aqueous sample, the process comprising:
 providing an aqueous sample containing the chemical species;   mixing the aqueous sample with a first reagent that comprises a solution of a molybdenum VI salt to provide a first solution;   mixing the first solution with a second reagent that comprises a reducing agent to form a second solution;   measuring a property of the second solution to determine the concentration of the chemical species; and   adding polyvinylpyrrolidone to the aqueous sample, the first reagent, the first solution or the second solution.   
     
     
         2 . The process of  claim 1 , wherein the polyvinylpyrrolidone is added to the first reagent. 
     
     
         3 . The process of  claim 2 , wherein the first reagent comprises no more than 1% (w/v) polyvinylpyrrolidone. 
     
     
         4 . The process of  claim 1 , wherein the polyvinylpyrrolidone is added to the second reagent. 
     
     
         5 . The process of  claim 4 , wherein the second reagent comprises no more than 1% (w/v) polyvinylpyrrolidone. 
     
     
         6 . The process of  claim 1 , wherein the second solution comprises no more than 0.5% polyvinylpyrrolidone. 
     
     
         7 . The process of  claim 1 , wherein the mass of polyvinylpyrrolidone corresponds to at least 10% of the mass of the molybdenum VI salt. 
     
     
         8 . The process of  claim 1 , wherein the chemical species is selected from (i) phosphate, (ii) arsenate or (iii) germanate. 
     
     
         9 . The process of  claim 1 , wherein the aqueous sample is saline. 
     
     
         10 . The process of  claim 1 , wherein molybdenum VI salt comprises ammonium molybdate and/or sodium molybdate. 
     
     
         11 . The process of  claim 1 , wherein the reducing agent is ascorbic acid or tin chloride. 
     
     
         12 . The process of  claim 1 , wherein measuring the property of the second solution comprises measuring the intensity of light that is transmitted or absorbed by the second solution. 
     
     
         13 . The process of  claim 1 , wherein (i) the first solution is a yellow solution and/or (ii) the second solution is a blue solution. 
     
     
         14 . The process of  claim 1  further comprising an initial step of obtaining the aqueous sample from industrial water or agricultural water or waste water or water for aquaculture or a body of water selected from an ocean, a sea, an estuary, a river, a reservoir, a lake, a ditch or a pond. 
     
     
         15 . The process of  claim 1 , further comprising an initial step of oxidizing the aqueous sample. 
     
     
         16 . The process of  claim 1 , wherein the second solution has a volume of no more than 100 ml, preferably no more than 1 mL. 
     
     
         17 . The process of  claim 1 , which is carried out on a lab-on-chip device. 
     
     
         18 . The process of  claim 1 , which is carried out on an analyser selected from a micro-fluidic sensor, a stopped flow analyser, a segmented flow analyser, a flow injection analyser, or a continuous flow analyser. 
     
     
         19 . An apparatus for measuring a concentration of a chemical species in an aqueous sample comprising a first vessel having a first reagent therein and a second vessel having a second reagent therein, the first reagent comprising a solution of molybdenum VI salt and the second reagent comprising a reducing agent, wherein at least one of the first reagent and the second reagent comprises polyvinylpyrrolidone. 
     
     
         20 . The apparatus of  claim 19 , additionally comprising a lab-on-chip device.